The application generally relates to a heat exchanger. The application relates more specifically to an air-cooled condenser for a heating, ventilation, air conditioning and refrigeration (HVAC&R) system having stacked coil sections operating at different condensing temperatures and/or pressures.
In HVAC&R systems, a refrigerant gas is compressed by a compressor and then delivered to the condenser. The refrigerant vapor delivered to the condenser enters into a heat exchange relationship with a fluid, e.g., air or water, and undergoes a phase change to a refrigerant liquid. The liquid refrigerant from the condenser flows through a corresponding expansion device(s) to an evaporator. The liquid refrigerant in the evaporator enters into a heat exchange relationship with another fluid, e.g. air, water or other process fluid, and undergoes a phase change to a refrigerant vapor. The other fluid flowing through the evaporator is chilled or cooled as a result of the heat-exchange relationship with the refrigerant and can then be used to cool an enclosed space. Finally, the vapor refrigerant in the evaporator returns to the compressor to complete the cycle.
In an air-cooled condenser, the refrigerant flowing through the condenser can exchange heat with circulating air generated by an air moving device such as a fan or blower. Since circulating air is used for heat exchange in an air-cooled condenser, the performance and efficiency of the condenser, and ultimately the HVAC&R system, is subject to the ambient temperature of the air that is being circulated through the condenser. As the ambient air temperature increases, the condensing temperature (and pressure) of the refrigerant in the condenser also increases. At very high ambient air temperatures, i.e., air temperatures greater than 110 degrees Fahrenheit (° F.), the performance and efficiency of the HVAC&R system can decrease due to higher condensing temperatures (and pressures) caused by the very high ambient air temperatures.
Therefore, what is needed is an air-cooled condenser that can operate at a lower condensing temperature at very high ambient air temperatures to maintain desired HVAC&R system performance and efficiency.